This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This proposed research addresses the significant clinical problem of osteopenia in children with cerebral palsy (CP). Children with CP frequently grow slowly. The impact of this altered growth on skeletal development and bone density is a significant health problem. In normally growing children, the accrual of peak bone mass follows peak height velocity. However, in children with CP, differences in linear growth become more accentuated over time when compared to those of normally growing peers. In addition, as growth slows, the bone mineral density also falls further outside the range of normal. Optimizing the accrual of bone mass during pre-pubertal growth likely will affect peak bone mass during puberty. Bone growth, as assessed by bone mineral density, is an important aspect of growth in children with CP. In addition to diminished linear growth, children with CP often sustain painful, pathologic fractures due to poor mineralization of bone. This often occurs with minimal trauma. Thus, bone growth and bone density are highly relevant to overall linear growth, nutritional health, and health-related quality of life. Significantly decreased bone density is virtually universal in non-ambulatory children with moderate-severe CP after age 10. Predicting who is at the highest fracture risk is a challenge. Studies have found the rate of fractures in children with CP to range from 12-26%. Multiple factors predispose children with disabilities for fragility fractures. These include lack of weight bearing activity, muscle mass, calcium and phosphate homeostasis, nutrition, and medication use, especially glucocorticoids and anticonvulsants. The natural history of bone accrual into and through adolescence has not been the focus of prior research. The goal of this pilot proposal is to longitudinally evaluate height velocity and bone mineral density accrual in 50 pre-pubertal children with CP and compare to a cohort of typically growing children. The investigators will use two techniques to assess bone accrual rates. Dual energy X-ray absorptiometry (DXA) is a 2D technique for assessing bone density but is limited in its ability to capture changes in bone size/structure. Peripheral Quantitative Computed Tomography (pQCT) is a novel technique which measures 3-D bone structure/density. It may offer superior technique for capturing changes in bone size and will be compared to the rates of accrual determined by the more standard technique of DXA. No longitudinal research exists in the measurements of bone density and strength using pQCT in children with CP.